Hydrogen oxidation reaction polarization

Fig. 3.3 Surface modification with Pd thin films by UHV vapor deposition (Left) Gold surface modified with Pd thin film (a) Rotating disc electrode (RDE) polarization curves for electrochemical hydrogen oxidation reaction on pure Au(lll), Au(lll)-Pd (for different rpm ) and Pt(lll) surfaces [51] (b) and (c) LEIS spectra of Au(lll)-Pd surfaces after vapor deposition of Pd in the amount that corresponds to four atomic monolayers. (Right) Platinum surface modified with Pd thin film (d) LEIS spectra of the Pt(l 11)-Pd surface with 65% of Pd and (e) LEIS spectra of Pd monolayer on Pt(lll) (red line) and pure Pt(lll) (dashed line), (a) Reprinted with permission from [51], copyright 2002 Elsevier...

In this section, we construct several analytical polarization curves of PEMFCs and high-temperature polymer electrolyte membrane fuel cells (HT-PEMFCs). In these types of cell, owing to the excellent kinetics of the hydrogen oxidation reaction, the polarization voltage of the anode is negHgible. The voltage loss in a PEMFC is determined by the oxygen transport, ORR kinetics, and the cell resistivity. 

The kinetics of the hydrogen oxidation reaction (HOR) (1.1) are very fast and the respective polarization voltage can be ignored. However,... 

The oxidation reaction polarizes iron in the anodic direction and the reduction reaction in the cathodic direction. The point of intersection gives icorr- The magnitude of over-voltage from the reversible potential is given by t/c for cathodic polarization and by jja for anodic polarization. Hydrogen is liberated and iron is corroded as Fe " ". 

Note that by definition, in electrochemistry, the reversible potential of the hydrogen oxidation reaction is zero at all temperatures [5]. That is why the standard hydrogen electrode is used as a reference electrode. Therefore, for hydrogen anodes E,a = OV. Activation polarization of the hydrogen oxidation reaction is much smaller than activation polarization of the oxygen reduction reaction. 

Fig. 10-16. Polarization curves for anodic oxygen and cathodic hydrogen redox reactions on an n-type semiconductor electrode of titanium oxide in the dark and in a photoex-cited state i = anodic current in the dark (zero) = anodic current...

Alcohols, ketones, and acids are formed as intermediates in the liquid phase oxidation of hydrocarbons [1] and are subject to further conversions. Therefore, investigation of the mechanisms of such conversions is necessary for the correct understanding of hydrocarbon oxidation. Moreover, the oxidation of alcohols and ketones is of scientific interest proper. The role of polar media and hydrogen bonding in chain oxidation is studied, particularly for alcohols and ketones. Alcohols are very convenient for the investigation of ionic oxidation reactions. The oxidation of certain alcohols is of interest for technology. For example, acetic acid and ethyl acetate may be produced by the oxidation of ethanol, and acetone and hydrogen peroxide by the oxidation of 2-propanol. 

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